Smartbitt SBOL50KTIII-3, Service Manual

Page: 7 / 57

7
4. Working Principle of the Major Functional Block
4.1 Switch Power Supply
The Switch Power Supply (SPS) supplies DC power for UPS operation. The input source of the SPS is
the battery, or the output of the charger.
Figure 4.1.1 Basic circuit of power supply for 10K-20K
Figure 4.1.2 Basic circuit of power supply for 30K-80K
Figure 4.1.1 is a flyback converter. When Q1 is on, rectifier diodes (D11/D12) are on open status and
output capacitors (C6/C7) supply currents to the load. The primary coil of the transformer will become a
pure inductor and the primary current will linearly increase to store energy in the coil. When Q1 is off,
primary current will stop and rectifier diodes (D11/D12) will turn to “close” status. It will release the stored
energy from the primary coil of the transformer to the secondary coil to supply loads. At the same time, it
will charge output capacitors including
±
12V, +5V, +12V(Fan), and HFPW
±
.
Figure 4.1.2 is a double tube flyback converter. When Q1 and Q2 are on, rectifier diodes (D11/D12) are
on open status and output capacitors (C6/C7) supply currents to the load. The primary coil of the
transformer will become a pure inductor and the primary current will linearly increase to store energy in
the coil. When Q1 and Q2 are off, primary current will stop and rectifier diodes (D11/D12) will turn to
“close” status. It will release the stored energy from the primary coil of the transformer to the secondary
coil to supply loads. At the same time, it will charge output capacitors including
±
12V, +5V, +12V(Fan),
and HFPW
±
.
The power of
±
12V, +5V supplies stable voltage to all kinds of ICs and other devices such as HCT. The
+12V (Fan) is supplied to fans and relays. The HFPW
±
supplies a high frequency power for the switch
(SCR/IGBT) driver and some other drive boards.
Battery
R LINE
S LINE
T LINE
SPS_BUS-
Q1
TX
+12V Output
-12V Output
D1
D2
D3
D4
D5
D6
D7
D8
D11
D12
D11
D12
C3
C4
C6
C7
BUS
D9
D10
C1
C2
D13
C5
R1
Battery
R LINE
S LINE
T LINE
SPS_BUS-
Q1
Q2
TX
+12V Output
-12V Output
D1
D2
D3
D4
D5
D6
D7
D8
D11
D12
D11
D12
C3
C4
C6
C7
BUS
D9
D10
C1
C2
D13
D14